the term pleiotropy is best defined as which of the following

HESI RN

Biology Test

1. The term pleiotropy is best defined as which of the following?

A. A situation in which one gene remains unexpressed
B. One gene influencing multiple, seemingly unrelated phenotypic traits
C. Two genes affected by a single allele
D. A condition in which multiple genes are missing

Correct answer: B

Rationale: Pleiotropy is best defined as one gene influencing multiple, seemingly unrelated phenotypic traits. This phenomenon showcases the multifunctionality of genes, where a single gene can have effects on various aspects of an organism's phenotype. Choices A, C, and D do not accurately capture the concept of pleiotropy. Option A refers to gene expression, not pleiotropy. Option C describes genetic interactions but not in the context of pleiotropy. Option D talks about missing genes, which is unrelated to the definition of pleiotropy.

2. The cellular membrane contributes to all except which of the following?

A. Cell energy production
B. Cell permeability
C. Cell communication
D. Cell protection

Correct answer: A

Rationale: The cellular membrane is involved in regulating cell permeability, communication, and protection. However, it is not directly involved in energy production. Choice A is the correct answer because the cellular membrane does not produce energy; instead, it regulates the passage of molecules in and out of the cell. Choices B, C, and D are incorrect because the cell membrane plays key roles in controlling what enters and exits the cell, facilitating communication between cells, and providing structural support and protection to the cell.

3. Which of the following molecules contains the code required for replication?

A. Deoxyribonucleic acid (DNA)
B. Transfer RNA (tRNA)
C. Messenger RNA (mRNA)
D. Ribonucleic acid (RNA)

Correct answer: A

Rationale: The correct answer is A: Deoxyribonucleic acid (DNA). DNA contains the genetic information essential for replication, ensuring the accurate transmission of genetic material from one generation to the next. Choice B, Transfer RNA (tRNA), is involved in protein synthesis, not replication. Choice C, Messenger RNA (mRNA), carries genetic information from DNA to the ribosome but does not contain the code for replication. Choice D, Ribonucleic acid (RNA), is a broader category that includes both mRNA and tRNA, but the specific molecule containing the code required for replication is DNA.

4. What characteristic of water allows for hydrogen bonding between molecules?

A. Its covalent bonds
B. Its cohesive properties
C. Its high specific heat
D. Its polar nature

Correct answer: D

Rationale: The correct answer is D: Its polar nature. Water is a polar molecule with a partial positive charge on hydrogen atoms and a partial negative charge on oxygen atoms. This polarity allows water molecules to form hydrogen bonds with each other. Choice A, covalent bonds, is incorrect because while water indeed has covalent bonds, they do not directly enable hydrogen bonding. Choice B, cohesive properties, is incorrect as cohesion refers to water's ability to stick to other substances, not the specific characteristic that allows for hydrogen bonding. Choice C, high specific heat, is also incorrect as it refers to water's ability to resist changes in temperature, not its property that leads to hydrogen bonding.

5. What percentage of the parents' offspring is predicted to have a cleft chin if one parent carries the recessive gene for a cleft chin (c) while the other parent does not?

A. 25%
B. 50%
C. 0%
D. 75%

Correct answer: C

Rationale: The correct answer is C (0%). If one parent carries the recessive gene for a cleft chin while the other parent does not carry it, none of their offspring is predicted to have a cleft chin. This is because the cleft chin trait is recessive, so for an offspring to express this trait, they would need to inherit the gene from both parents. In this scenario, none of the offspring will inherit the recessive gene from both parents, so the percentage of offspring predicted to have a cleft chin is 0%. Choices A, B, and D are incorrect because in this situation, the offspring will not express the cleft chin phenotype, although they could be carriers of the recessive gene.